1. Field of the Invention
The present invention relates to an optical switch for use in optical communication and optical network technology, and particularly to a mechanically operated optical switch with a rotatable prism as a switching element. A copending application having the same filing date, the same title, the same applicant and the same assignee with the invention, is referenced hereto.
2. Description of Related Art
Optical signals are commonly transmitted in optical fibers, which provide efficient light channels through which optical signals can pass. Recently, optical fibers have been used in various fields, including telecommunications, where light passing through an optical fiber is used to convey either digital or analog information. Efficient switching of optical signals between individual fibers is necessary in most optical processing systems or networks to achieve the desired routing of the signals.
In optical fiber systems, various methods have been previously developed for switching optical signals between fiber cables. Among these previously developed methods, one imcollimatorant category is mechanical optical switches.
Mechanically operated optical switches come in two different designs: in one design, the optical components move, and in the other design, the fibers move. Factors for assessing the capability of an optical switch include low insertion loss ( less than 1 dB), good isolation performance ( greater than 50 dB) and bandwidth capacity compatible with the fiber network that the switch is supporting.
Moving fiber switches involve the actual physical movement of one or more of the fibers to specific position to accomplish the transmission of light beams from one fiber end to another under selected switching conditions. Moving optical component switches, on the other hand, include optical collimating lenses which expand the light beam coming from the fibers, and then, using moving prisms or mirrors, redirect the expanded light beam to other fibers, as required by the switching process.
The moving fiber switches have a stringent tolerance requirement for the amount and direction of fiber movement. The tolerance is typically a small fraction of the fiber core diameter for two fibers to precisely collimate to reduce loss. The fibers themselves are quite thin and may be subject to breakage of not properly protected. On the other hand, reinforcing the fibers with stiff protective sheaths makes the fibers less flexible, increasing the force required to manipulate each fiber into alignment. Thus these moving fiber switches share a common problem of requiring high precision parts to obtain precise position control and low insertion loss. This results in high cost and complicated manufacture of the switches. Moreover, frequently moving fibers to and fro is apt to damage or even break the fibers.
The moving optical component switches, in contrast, have less stringent movement control tolerance requirements. The presence of collimating lenses allows relaxation of the tolerance requirements.
As illustrated in FIG. 6, U.S. Pat. No. 5,420,946, describes an optical coupling switch for coupling light from an input fiber 611 into a selected output collimator 620. The input fiber 611 is optically aligned with one of a plurality of output fibers 621 via a reflector 630. By rotating the reflector 630 about an axis, the input light beams can be reflected to a selected output fiber 621. The input fiber 611 and all the output fibers 621 are in fixed position relative to each other.
In this mechanical switch, the plurality of output fibers 621 are separately mounted on a platform 600, which makes the structure of the switch complex and large, and which do make the aligning process between the input fiber 611 and the plurality of output fibers 621 time consuming. In addition, this prior art mechanical switch uses a plurality of GRIN lenses (622, 612) on front ends of the output fibers 621 and the input fiber 611 to collimate the light beams. All the GRIN lens goatly add cost to the mechanical switch greatly.
For the above reasons, an improved optical switch is desired. In particularly, an optical switch is desired which has low cost, high optical efficiency and which does not require precise alignment or movement of the optical fibers themselves.
An object of the present invention is to provide an optical switch in which the optical fibers don""t move.
Another object of the present invention is to provide an optical switch which allows easy alignment of associated fibers and which has a high optical efficiency.
Yet another object of the present invention is to provide an optical switch which is low in cost and small in size.
An optical switch in accordance with one embodiment of the present invention, for switching light beams between one input optical fiber and a plurality of output optical fibers, comprises a first collimator aligning with the input optical fiber and collimating input light beams; a second collimator aligning with the output fibers and collimating output light beams; and a switching element between the first and second collimators comprising at least one rotatable optical element for deflecting the light beams and a holder for containing the rotatable optical elements, the rotatable optical element being rotatable among a plurality of positions; whereby, when the optical element is in different positions, the light beams from the input optical fiber are switched to different output fibers, respectively.
Other objects, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.